Not Applicable
Not Applicable
(1) Field of the Invention
The present invention relates to an apparatus and a method which use hydroforming to shape complex structures from materials such as sheet metal or composites. In particular, an apparatus and a method for shaping complex structures using composites such as continuous-fiber or woven fiber composites with limited wrinkling or rupture of the composite during the shaping process.
(2) Description of Related Art
Numerous manufacturing processes have been proposed over the years to shape composite materials, ranging from injection molding to sheet stamping, and filament winding. When reinforcements are incorporated into the matrix, ready-to-mold sheets can be prepared, stored, and processed later. The raw material thus processed comes in many forms, e.g., prepregs and sheet molding compounds (SMG) (Schwartz in Composite Materials: Processing, Fabrication and Applications. Prentice Hall, Upper Saddle River, N.J. 1997). The matrix is typically a thermosetting polymer, but thermoplastic-based fabrics and unidirectional sheets are also available for further processing. Shaping operations with these raw materials can be performed with sheet forming, bag molding, match die molding, contact molding, or transfer molding (Schwartz, ibid.). All these processes have been studied fairly extensively and are currently used by industry to manufacture polymer reinforced products of varying quality.
Various attempts have also been made to apply sheet stamping techniques to composites due to its high success with metals. A difficulty in using composite materials in stamping, however, is the limited draping capability of the fabrics or sheets. Forming of straight, continuous-fiber or woven-fiber composites results in wrinkling of the fibers and distortions. Randomly oriented fibers have provided good formability but without the advantages of the highly directional properties often desired in composite parts. Formable sheets that consist of aligned, discontinuous fibers appear to have been used with more success than continuous fibers (Okine et al., J. Reinforced Plastics Compos. 8: 70 (1990)). There is nonetheless a current need for forming and shaping methods that can produce complex structures with wrinkling limited as much as possible.
Hydroforming is a method that has been used for forming metals. Hydroforming consists of using a pressurized fluid to maintain the metal blank in close contact with the punch or die. This results, when compared with drawing of metals, in formation of metal components that have greater dimensional stability, in greatly reduced wrinkling, and reduced tooling and manufacturing costs (Hsu et al., J. Manuf. Sci. and Eng. 118: 434-438 (1996)). The following U.S. Patents relate to methods for using hydroforming to manufacture metal components.
U.S. Pat. Nos. 5,157,969 and 5,372,026 to Roper discloses an apparatus and method for hydroforming sheet metal using a modified standard double action press. U.S. Pat. No. 5,557,961 to Ni et al. discloses a method for hydroforming a tubular structural member of generally polygonal, flat-walled cross-section in which the various walls in the final part do not have the same thickness. U.S. Pat. No. 5,927,120 to Marando disclose a hydroforming apparatus that can deform relatively large and thick-walled workpieces. U.S. Pat. No. 6,067,831 to Amborn et al. discloses a hydroforming process for forming a component from an elongate tubular blank comprised of a deformable metal.
Since hydroforming for shaping metals has been shown to have important advantages over other metal shaping processes such as reduced tooling costs, increased drawability, and formation of components with greater dimensional stability, these same advantages could be realized for the manufacture of shaped composites by hydroforming if a coherent numerical method were available for predicting the final component geometry and for optimization of the hydroforming process for making shaped composites.
The present invention provides a hydroforming apparatus for forming a blank, the apparatus capable of being used in a conventional punch press comprising a fluid chamber mountable to an upper shoe defining a cavity for providing pressurized fluid to the upper surface of the blank and having a downwardly facing blank mating surface; a blank support mountable to a lower shoe having an upwardly facing blank binding surface for holding the blank with an opening therein which defines a cavity wherein a punch reciprocally located therein is capable of traveling upward through the opening into the fluid chamber; and the fluid chamber and blank support being adapted to receive and clamp a flexible blank between the blank mating surface and the blank binding surface, and the fluid chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the fluid chamber wherein the fluid contacts the blank and a release means for removing the fluid.
The present invention further provides a hydroforming apparatus for forming a blank, comprising a punch press comprising an upper shoe and a lower shoe with an opening therein which defines a cavity with a punch reciprocally located therein which is capable of traveling upward through the opening; a fluid chamber mounted on the upper shoe defining a cavity for providing pressurized fluid to the upper surface of the blank and having a downwardly facing blank mating surface; a blank support with an opening mounted on the lower shoe over the opening in the lower shoe and having an upwardly facing blank binding surface for holding the blank wherein the opening in the blank support enables the punch reciprocally located within the lower shoe to travel upward into the fluid chamber; and the fluid chamber and blank support being adapted to receive and clamp a flexible blank between the blank mating surface and the blank binding surface, and the fluid chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the fluid chamber wherein the fluid contacts the blank and a release means for removing the fluid.
Further still, the present invention provides a hydroforming apparatus for forming a blank, the apparatus capable of being used in a conventional punch press comprising a fluid chamber mountable to a first shoe defining a cavity for providing pressurized fluid to an obverse surface of the blank and having a blank mating surface; a blank support mountable to a second shoe having blank binding surface for holding a reverse surface of the blank with an opening therein which defines a cavity wherein a punch reciprocally located therein is capable of traveling through the opening into the fluid chamber; and the fluid chamber and blank support being adapted to receive and clamp a flexible blank between the blank mating surface and the blank binding surface, and the fluid chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the fluid chamber wherein the fluid contacts the blank and a release means for removing the fluid. Preferably, the upper shoe and the lower shoe are mounted in a punch press.
An further still, the present invention provides a hydroforming apparatus for forming a composite blank, the apparatus capable of being used in a conventional punch press comprising a fluid chamber mountable to a first shoe defining a cavity for providing pressurized fluid to an obverse surface of the blank and having a blank mating surface; a blank support mountable to a second shoe having a blank binding surface for holding a reverse surface of the blank with an opening therein which defines a cavity wherein a punch reciprocally located therein is capable of traveling through the opening into the fluid chamber; a recycle means to introduce heated or cooled fluid into the fluid chamber to cure the composite blank; and the fluid chamber and blank support being adapted to receive and clamp a flexible blank between the blank mating surface and the blank binding surface, and the fluid chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the fluid chamber wherein the fluid contacts the blank and a release means for removing the fluid.
In a particular embodiments of the above apparatus, the punch is enclosed within a punch chamber which has an opening for the punch to travel into the fluid chamber, wherein the punch chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the punch chamber wherein the fluid contacts the blank and a release means for removing the fluid.
It is preferable that the fluid be selected from the group comprising silicon-based oil, petroleum-based oil, or a plant-based oil and further that the pressurized fluid means comprises a pressurized reservoir wherein the pressurized fluid is provided to the passageway means and wherein the pressure of the fluid is controlled by a pressure regulator. In particular, wherein the pressure of the pressurized fluid is monitored by a pressure transducer. Preferably, wherein the pressure of the pressurized fluid is controlled by a computer.
In a preferred embodiment, there is further provided a heating means that heats fluid which is pressurized by the pressurized fluid means to a temperature between the glass transition temperature and melting temperature of the blank. Alternatively, or in addition to the above heating means, the present invention provides a heating means that heats the blank support to a temperature between the glass transition temperature and melting temperature of the blank.
In particular embodiments of the present invention, it is further provided that the apparatus comprise a membrane that is impervious to the pressurized fluid and which is positioned between the blank and the pressurized fluid to prevent the pressurized fluid from directly contacting the surface of the blank.
The present invention further provides a method for hydroforming a blank comprising (a) providing an apparatus mounted in a conventional press comprising a fluid chamber mounted on a first shoe defining a cavity for providing pressurized fluid to an obverse surface of the blank and having a blank mating surface; a blank support mounted to a second shoe having a blank binding surface for holding a verse surface of the blank with an opening therein which defines a cavity with a punch reciprocally located therein which is capable of traveling through the opening into the fluid chamber; and wherein the fluid chamber and blank support being adapted to receive and clamp a flexible blank between the blank mating surface and the blank binding surface, and the fluid chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the fluid chamber wherein the fluid contacts the blank and a release means for removing the fluid; (b) positioning a blank on the blank support between the blank mating surface and the blank binding surface; (c) forming a seal between the blank and the fluid chamber and the punch cavity by moving the fluid chamber toward the punch chamber until the blank is firmly clamped between the blank mating surface and the blank binding surface; (d) providing a fluid to the fluid chamber under a pressure sufficient to conform the blank to the shape of the punch as the punch moves into the cavity of the fluid chamber; (e) moving the punch into the cavity of the fluid chamber to form the blank to the shape of the punch; (f) removing the fluid through the release means; (g) withdrawing the punch into the punch cavity; and (h) removing a formed blank from the apparatus. The pressurized fluid is at a pressure sufficient to conform the blank to the punch as the punch deforms the blank.
The present invention also provides a method for hydroforming a composite blank comprising (a) providing an apparatus mounted in a conventional press comprising a fluid chamber mounted on a first shoe defining a cavity for providing pressurized fluid to an obverse surface of the blank and having a blank mating surface; a blank support mounted to a second shoe having a blank binding surface for holding a verse surface of the blank with an opening therein which defines a cavity with a punch reciprocally located therein which is capable of traveling through the opening into the fluid chamber; and wherein the fluid chamber and blank support being adapted to receive and clamp a flexible blank between the blank mating surface and the blank binding surface, and the fluid chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the fluid chamber wherein the fluid contacts the blank and a release means for removing the fluid; (b) positioning a blank on the blank support between the blank mating surface and the blank binding surface; (c) forming a seal between the blank and the fluid chamber and the punch cavity by moving the fluid chamber toward the punch chamber until the blank is firmly clamped between the blank mating surface and the blank binding surface; (d) providing a fluid to the fluid chamber under a pressure sufficient to conform the blank to the shape of the punch as the punch moves into the cavity of the fluid chamber; (e) moving the punch into the cavity of the fluid chamber to form the blank to the shape of the punch; (f) removing the fluid through the release means; (g) withdrawing the punch into the punch cavity; (h) providing heated or cooled fluid to the fluid chamber through a recycle means to cure the composite comprising the blank; and (i) removing a formed blank from the apparatus. The pressurized fluid is at a pressure sufficient to conform the blank to the punch as the punch deforms the blank.
In a preferred embodiment, the punch is enclosed within a punch chamber which has an opening for the punch to travel upwards into the fluid chamber, wherein the punch chamber includes a passageway means for transmitting pressurized fluid from a pressurized fluid means to the punch chamber wherein the fluid contacts the blank and a release means for removing the fluid and wherein the pressurized fluid pressure is at a pressure sufficient to maintain equal pressure on both sides of the blank during the blank forming. In either embodiment, it is preferable that the pressurized fluid means comprise a pressurized reservoir wherein the pressurized fluid is provided to the passageway means and wherein the pressure of the fluid is controlled by a pressure regulator. It is further preferable that the pressure of the pressurized fluid be monitored by a pressure transducer and that the pressure of the pressurized fluid be controlled by a computer. It is also preferable that the fluid is selected from the group consisting of silicon-based oil, petroleum-based oil, or a plant-based oil and that the pressurized fluid be provided at a temperature between the glass transition temperature and the melting temperature of the blank.
In particular embodiments of the present invention, a membrane, which is impervious to the pressurized fluid, is positioned between the blank and the pressurized fluid to prevent the pressurized fluid from directly contacting the surface of the blank.
During the forming of the blank the fluid pressure can be maintained at a constant pressure or the fluid pressure is varied over time. In particular embodiments, the blank is heated to a temperature between its glass transition temperature and its melting temperature. In a preferred embodiment, an infra-red heater is used to heat the blank. In particular embodiments, the blank support is heated to a temperature between the glass transition temperature and melting temperature of the blank.
The method of the present invention is useful for hydroforming blanks which comprise a metal or a composite and is particularly useful for hydroforming composite blanks which are brittle at or below room temperature.
It is an object of the present invention to provide an apparatus for hydroforming. In particular, an apparatus to shape complex structures using composites such as continuous-fiber or woven fiber composites with limited wrinkling or rupture of the composite during the shaping process.
It is further an object of the present invention to provide a method for hydroforming. In particular, a method to shape complex structures using composites such as continuous-fiber or woven fiber composites with limited wrinkling or rupture of the composite during the shaping process.